Stackable wall block



FIG. 1 is a perspective view of a stackable wall block showing my new design.

FIG. 2 is a front view thereof.

FIG. 3 is a rear view thereof.

FIG. 4 is a bottom view thereof.

FIG. 5 is a top view thereof; and,

FIG. 6 is a side view thereof.

The broken lines appearing in the figures are not intended to form part of the claimed design and are provided for illustrative purposes only. 

I claim the ornamental design for a stackable wall block, as shown. 